Fundamental Types
Fundamental types in C++ are divided into three categories: “integral,” “floating,” and “void.” Integral types are capable of handling whole numbers. Floating types are capable of specifying values that may have fractional parts.
The void type describes an empty set of values. No variable of type void can be specified — it is used primarily to declare functions that return no values or to declare “generic” pointers to untyped or arbitrarily typed data. Any expression can be explicitly converted or cast to type void. However, such expressions are restricted to the following uses:
- An expression statement. (See Chapter 4, Expressions, for more information.)
- The left operand of the comma operator. (See Comma Operator in Chapter 4 for more information.)
- The second or third operand of the conditional operator (? :). (See Expressions with the Conditional Operator in Chapter 4 for more information.)
Table 2.3 explains the restrictions on type sizes. These restrictions are independent of the Microsoft implementation.
Table 2.3 Fundamental Types of the C++ Language
| Category | Type | Contents |
|---|---|---|
| Integral | char | Type char is an integral type that usually contains members of the execution character set — in Microsoft C++, this is ASCII. |
| The C++ compiler treats variables of type char, signed char, and unsigned char as having different types. Variables of type char are promoted to int as if they are type signed char by default, unless the /J compilation option is used. In this case they are treated as type unsigned char and are promoted to int without sign extension. | ||
| bool | Type bool is an integral type that can have one of the two values true or false. Its size is unspecified. | |
| short | Type short int (or simply short) is an integral type that is larger than or equal to the size of type char, and shorter than or equal to the size of type int. | |
| Objects of type short can be declared as signed short or unsigned short. Signed short is a synonym for short. | ||
| int | Type int is an integral type that is larger than or equal to the size of type short int, and shorter than or equal to the size of type long. | |
| Objects of type int can be declared as signed int or unsigned int. Signed int is a synonym for int. | ||
| __intn | Sized integer, where n is the size, in bits, of the integer variable. The value of n can be 8, 16, 32, or 64. | |
| long | Type long (or long int) is an integral type that is larger than or equal to the size of type int. | |
| Objects of type long can be declared as signed long or unsigned long. Signed long is a synonym for long. | ||
| Floating | float | Type float is the smallest floating type. |
| double | Type double is a floating type that is larger than or equal to type float, but shorter than or equal to the size of type long double.1 | |
| long double1 | Type long double is a floating type that is equal to type double. |
1 The representation of long double and double is identical. However, long double and double are separate types.
Microsoft Specific
Table 2.4 lists the amount of storage required for fundamental types in Microsoft C++.
Table 2.4 Sizes of Fundamental Types
| Type | Size |
|---|---|
| bool | 1 byte |
| char, unsigned char, signed char | 1 byte |
| short, unsigned short | 2 bytes |
| int, unsigned int | 4 bytes |
| long, unsigned long | 4 bytes |
| float | 4 bytes |
| double | 8 bytes |
| long double1 | 8 bytes |
1 The representation of long double and double is identical. However, long double and double are separate types.
For more information about type conversion, see Chapter 3, Standard Conversions.